Bicondylar knee resurfacing prosthesis

ABSTRACT

A bicondylar knee resurfacing prosthesis for limited knee resurfacing procedure inserted through a direct mini lateral approach, which avoid disruption of the extensor mechanism or damage to the quadriceps tendon. The inventive device includes a reduced femoral component, a metallic tibial tray and a polyethylene tibial insert. 
     A metallic reduced femoral component having a thin polished convex articular surface in a form of two condyles, medial and lateral, connected with an intercondylar bridge. The concave surface having a metallic dovetail transverse ridge across the entire width of the femoral component precisely positioned at the level of maximum weight bearing contact in full extension. The concave surface provides fine asperities and voids to allow bone ingrowth or can be cemented using conventional methyl methacrylate bone cement. 
     The tibial tray provides a dovetail recess along the superior surface and transversely across its entire width, which will slidingly receive the polyethylene tibial insert. The bottom surface of the metallic tibial tray in contact with the tibial plateau has a dovetail ridge, which extends transversely along the entire width of the tibial component securing the tibial component to the resected tibial plateau. 
     The tibial insert is made of polyethylene and has the same shape and size of the tibial metallic tray. It provides a dovetail that matches the one on the tibial tray so it can be easily driven in and locked in place. The surface of the tray provides two shallow condylar grooves that conformably match the condylar convex surfaces of the metallic femoral component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from prior U.S. Provisional Application No. 60/860,409 filed Nov. 21, 2006. The entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to knee resurfacing prosthesis and more specifically it relates to a bicondylar knee resurfacing prosthesis for bicompartmental knee resurfacing, which is inserted through a limited and minimally invasive lateral approach, without any disruption of the extensor mechanism or damage to the quadriceps tendon.

2. Description of the Related Art

It can be appreciated that knee-resurfacing prostheses have been in use for years to treat articular surfaces destroyed by arthritis or pathological processes secondary to trauma. Basically, the natural knee joint comprises an upper femoral articular surface having two condylar surfaces and a lower tibial plateau comprising two cupules shaped tibial condyles articulating smoothly with the upper femoral condyles. Typically, knee replacement prostheses are comprised of several types of prostheses, where articular compartments of the knee are removed and replaced with metal and polyethylene components.

The devices of prior art attempted to duplicate the geometry of the natural articular surface, where the femoral component have a semicircular C shaped device such as depicted in a U.S. Pat. No. 4,224,696. The bicondylar design is similarly disclosed in prior patents by F. Buechel and Pappas in U.S. Pat. Nos. 4,309,778 and 4,470,158. More recent bicondylar design is described in U.S. Pat. No. D473,307S and U.S. Pat. No. 6,197,064 B1. The prior art describes the bicondylar prosthesis as having a middle patellar groove for the femoral patellar articulation. Other knee resurfacing devices are used to resurface only one femoral condyle such as unicondylar prostheses described in U.S. Pat. No. 7,141,053; U.S. U.S. Pat. No. 6,726,724B2,

Most unicondylar devices used septum, pegs and alike for fixation. The unicondylar design as described in U.S. Pat. No. 6,299,645 B1 used multiple dovetail pegs for fixation to one femoral condyle.

However, unicondylar prostheses in general present a high rate of failure due to loosening and dislocation secondary to poor distribution of weight and high concentration of stress over a small surface. Furthermore, almost all the patents cited above described prostheses that are inserted through a conventional anterior, anteromedial or anterolateral surgical approach.

The main problem with conventional knee resurfacing prostheses is the fact that the surgical approach used during their insertion causes extensive soft tissue disruption and irreparable scarring to major anatomical structures. Another problem with conventional knee resurfacing prostheses is the anterior surgical approach that violates the extensor mechanism of the knee joint namely the quadriceps muscle, quadriceps tendon and the extensor retinaculum. Another problem with conventional knee resurfacing prostheses is the need to laterally dislocate and “flip” over the patella and the patellar tendon in order to access both condyles, which frequently weakens the insertion of the patellar tendon, causing undue pain in the immediate post operative period.

While these devices may be suitable for the particular purpose to which they address they are, because of their size, not suitable for bicondylar knee resurfacing through a limited lateral approach, without disrupting the extensor mechanism or damaging the quadriceps tendon. The main problem with conventional knee resurfacing prostheses is the fact that the both condyles are approached anteriorly through a medial or lateral para patellar approach, which causes extensive soft tissue disruption and irreparable scarring to major anatomical structures by violating the extensor mechanism of the knee joint namely the quadriceps muscle and tendon.

Another problem is the large size of the femoral component of the conventional prosthesis, which makes it very difficult to insert through a limited true lateral approach that is appropriately described for the prosthesis of this invention. The prosthesis of this invention is thinner and much smaller than the conventional total knee femoral component, since it does not address the femoro-patellar joint.

In these respects, the bicondylar knee resurfacing prosthesis according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for the purpose of resurfacing the articular surfaces of the femur and the tibia through a limited and true lateral approach, without disruption of the extensor mechanism or damage to the quadriceps tendon. Furthermore, the prosthesis of the present invention does not address the patello femoral joint such as other conventional devices and hence, is much thinner and smaller in size.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages inherent in the known types of knee resurfacing prosthesis now present in the prior art, the present invention provides a new bicondylar knee resurfacing prosthesis construction wherein the same can be utilized for a bicondylar knee resurfacing procedure inserted through a small direct lateral approach, without disruption of the extensor mechanism or damage to the quadriceps tendon.

The general purpose of the present invention, which will be described subsequently in greater detail, is to provide a new bicondylar knee resurfacing prosthesis that has many of the advantages of the knee resurfacing prosthesis mentioned heretofore and many novel features that result in a new mini bicondylar knee resurfacing prosthesis which is not anticipated, rendered obvious, suggested, or even implied by any of the prior art knee resurfacing prosthesis, either alone or in any combination thereof.

To attain this, the present invention generally comprises a metallic femoral component retaining the anatomical geometry, reduced in size to match the weight-bearing portion of both femoral condyles, a metallic tibial tray and a polyethylene tibial insert.

The metallic femoral component having a curved arcuate polished convex articular surface in a form of two condyles, medial and lateral which are connected together by an intercondylar bridge. The concave surface having a femoral fixation means in the form of a straight metallic transverse ridge. Said ridge has the shape of a dovetail in its cross section and extends along the entire width of the femoral component. Said component having a thickness between 2 millimeters at its thinner posterior condylar region and 6 millimeters at the thickest weight-bearing portion.

In addition, the concave surface provides fine asperities and voids to allow bone ingrowth. The concave surface can also be cemented using conventional methylmethacrylate bone cement.

A metallic tibial tray which will be inserted laterally through a mini incision in the lateral quadrilateral space delineated in FIG. 1, having a bottom surface to be affixed to the tibial plateau. Said bottom surface has a fixation means in the form of a dove tail retaining ridge. Said dovetail fixation means extends transversely along the entire width of the metallic tray. The top surface provides a transverse recess in a form of dovetail retaining groove to hold the polyethylene tibial insert. Said dovetail retaining groove is positioned transversely along the entire width of the metallic tibial tray, so that the polyethylene tray can be slidingly inserted laterally through a mini incision in the quadrilateral space.

Once slid into the tibial dove tail groove, the polyethylene tray will be firmly retained by a locking mechanism comprising a small recess in the metallic tibial tray and a corresponding protruding tang provided at the bottom of the polyethylene tray. This will allow the polyethylene component to lock in place after complete insertion and prevents it from moving out once it is locked in.

[There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter.

In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

A primary object of the present invention is to provide a bicondylar knee resurfacing prosthesis for a bicondylar knee resurfacing that is limited to the weight-bearing and the arc of motion area between the tibia and the femur, which is inserted through a limited lateral direct approach, situated within the lateral quadrilateral space and without disruption of the extensor mechanism or damage to the quadriceps tendon. It provides a bicondylar knee resurfacing prosthesis that will overcome the shortcomings of the prior art devices.

Other objects and advantages of the present invention will become obvious to the reader and it is intended that these objects and advantages are within the scope of the present invention.

To the accomplishment of the above and related objects, this invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 is a side view of the normal bony anatomical structures of the knee joint in full flexion revealing the quadrilateral space.

FIG. 2 is a side view of the normal bony structures of the knee joint flexion after preparation of the femoral and tibial articular surfaces and burring the dove tail grooves.

FIG. 3 is a side view of the femoral metallic prosthetic component revealing the retaining dovetail ridge.

FIG. 4 is a antero lateral view of the femoral component exposing the transverse dovetail retaining ridge.

FIG. 5 is an antero lateral view of the femoral component inserted onto the femur.

FIG. 6 is a cross sectional view of the tibial metallic component.

FIG. 7 is a cross sectional view of the polyethylene insert.

FIG. 8 is an anteromedial view of the resected tibial plateau showing the tibial dove tail groove ready to receive the tibial metallic tray.

FIG. 9 is an anteromedial view of the tibial plateau showing the metallic tibial tray inserted in place.

FIG. 10 is an anteromedial view of the tibial plateau showing the metallic tibial tray and the polyethylene tibial tray inserted in place into their correspondent dovetail grooves.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT

Turning now descriptively to the drawings, in which similar reference characters denote similar elements throughout the several views, the attached figures illustrate a concise bicondylar knee resurfacing prosthesis, which comprises a thin metallic femoral arcuate component, a metallic tibial tray and a polyethylene tibial insert.

An arcuate metallic femoral component having a polished convex articular surface in a form of two condyles, medial 28 and lateral 25 that are connected with an intercondylar bridge 16.

The preferred embodiment of the present invention is a concise thin shell like bicondylar metallic arcuate component having a thickness between 2 millimeters at its thinner posterior condylar region 18 and 6 millimeters at the thickest weight bearing portion 17.

The concave surface having a metallic transverse ridge 14. Said ridge has the shape of a dovetail in its section and extend along the entire width of the femoral component, as depicted in FIG. 4. Said dovetail retaining ridge has 20° angles between the two-sloped sides.

The height of the ridge is approximately 12 millimeters, and measures approximately 5 millimeters at its narrow base in contact with the body of the femoral component. At the outer or lateral end of the dovetail ridge, an orifice 26 allows the attachment of insertion tools.

In another preferred embodiment of the present invention, the angle between the two slopped sides of the dovetail ridge is reduced to zero degree, so that said slopped surfaces become parallel and subsequently the dovetail ridge becomes a fin like transverse ridge. More than one perpendicular fin can be provided in order to increase the stability of the femoral component.

The concave surface provides fine asperities and voids to allow bone ingrowth, which will solidly affix the femoral metallic component to bone. Said femoral metallic component can also, if need arise, be cemented to the femur using conventional methyl methacrylate bone cement.

A metallic tibial tray 19 having a flat top and bottom surfaces. As shown in FIG. 6, the top surface provides a recess 21 in the form of dovetail for the purpose of securely retaining the polyethylene tibial insert. Said dovetail recess runs transversely across the entire flat width of the metallic tibial tray and stops one quarter of an inch short of the medial edge of the metallic tibial tray, as shown in FIG. 9.

The bottom surface of the metallic tray, which is in contact with tibial plateau, has a metallic ridge 20 having the shape of a dovetail, which runs transversely across the entire width of the bottom surface of the metallic tibial tray, as shown in FIG. 6.

The height of the ridge is approximately 12 millimeters, and measures approximately 5 millimeters at its narrow base in contact with the body of the tibial component. Said dovetail ridge has 20° angles between the two-sloped sides. The tibial tray may or may not be cemented to the tibia using conventional bone cement.

In another preferred embodiment of the present invention, the angle between the two slopped sides of the dovetail ridge is reduced to zero degree, so that said slopped surfaces become parallel and subsequently the dovetail ridge becomes a fin like transverse ridge. More than one perpendicular fin can be provided in order to increase the fixation and the stability if the component.

The tibial insert 22 is made of polyethylene and has the same shape and size of the tibial metallic tray as shown in FIG. 7. The top surface, which articulates with the femoral component, provides two cupules or shallow condylar grooves 24 that conformably match the condylar convex surfaces of the metallic femoral medial and lateral condyles, as shown in FIG. 10.

The bottom surface of said polyethylene tibial insert having a dove tail configuration 23 that runs transversely and can slide conformably and easily into the corresponding top groove 21 of the metallic tibial tray as shown in FIG. 10.

In addition, the tibial insert has a locking mechanism in a form of a small lateral recess 27, situated at the lateral end of the dovetail groove 21, which will receive a small locking tab extending from the inferior surface of the polyethylene insert; locking it in place after insertion and preventing it from moving out once its it locked in, as shown in FIG. 10.

Initially, the knee joint is approached through a very limited lateral incision in the lateral quadrilateral space as shown in FIG. 1. The retropatellar region is approached directly and the infrapatellar fat pad is excised. Care is taken to avoid injury to the lateral collateral ligament, which is retracted posteriorly. The placement of appropriate jigs and cutting guides is facilitated by the use of computerized navigation systems which aids in appropriate positioning of the instrumentation based on digital extrapolation from the patient's knee CT scan. In view of the concise approach and limited incision, It is needless to state that the precise shaving and dovetail burring of the bone is greatly facilitated by the use of robot interfaced to a conventional navigation system

Total condylar resurfacing is made possible using the above-described technique and approaching the knee joint through a direct mini lateral approach. The approach is safe, noninvasive and spares the extensor mechanism and the quadriceps tendon. This will undoubtedly reduce the postoperative pain and provide a sooner return to normal activity.

As to a further discussion of the manner of usage and operation of the present invention, the same should be apparent from the above description. Accordingly, no further discussion relating to the manner of usage and operation will be provided.

With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 

1. An implantable bicondylar femoro-tibial prosthetic device for forming a joint between a patient's femur and tibia, comprising: (a) a femoral bicondylar metallic component having a convex articulating surface and a concave surface to be firmly attached and anchored to a resected surface of said femur; (b) a tibial metallic platform having a bottom surface which includes a transverse fixation ridge that will be embedded and affixed to a resected tibial surface; and (c) a polyethylene insert disposed between said metallic femoral and tibial components.
 2. The tibial component as claimed in claim 1, fabricated from a metal or metal alloy, having on bottom surface an integral metallic ridge in a form of a dovetail transversely situated along the entire width of said tibial component, whereby said metallic ridge allows firm retention of said metallic component onto the resected tibial bone.
 3. The tibial component as recited in claim 2, fabricated from a metal or metal alloy, having transversely situated dove tail recess on a top surface, which captively engages said polyethylene insert by means of dovetail configuration, wherein said transverse dovetail recess runs across the entire width of said metallic component and stops few millimeters short of a medial border of said metallic tray.
 4. The tibial dovetail fixation means as claimed in claim 2, is approximately 12 mm high and has a 20 degrees angle between two-sloped sides.
 5. Said angle as claimed in claim 4 can be reduced to 0 degrees where said two sloped sides become parallel and said dovetail becomes a transverse coronal fin, which will be embedded in resected and prepared tibial bone.
 6. A femoral bicondylar thin metallic component of claim 1 further comprising two elongated longitudinally-convexly-curved articulating surface adapted for affixing to the prepared femoral surface by means of a dovetail ridge.
 7. Said elongated longitudinally-convexly-curved articulating surfaces as claimed in claim 6 are connected in the intercondylar region by an integral bridge.
 8. The affixing means as claimed in claim 6 is an integral dovetail ridge, which runs transversely along an entire width of said femoral component, where said ridge is located at the level of the intercondylar bridge, which correspond to the maximum weight-bearing area when said patient's knee is in full extension.
 9. Said dovetail fixation ridge as claimed in claim 6, is approximately 10 mm high and forms approximately 20 degrees angles between two sloped sides.
 10. The dovetail fixation means as claimed in claim 4, wherein said angle of said tibial dovetail fixation means is capable of being reduced to 0 degrees where said two sloped sides become parallel and said dovetail becomes a transverse coronal fin wherein one or more fins are provided to enhance fixation.
 11. The femoral component as claimed in claim 6, has at least one small lateral opening provided for attachment of insertion tools.
 12. A polyethylene insert as recited in claim 1, fabricated from conventional polyethylene, wherein said insert has an exact shape of a tibial metallic tray and provides a transverse dove tail retaining ridge on said bottom surface which is captively engaged in a recess on a top surface of a metallic tray by means of dovetail configuration allowing firm retention to said metallic tibial platform.
 13. A polyethylene insert as recited in claim 1, where said dovetail ridge situated on said bottom surface runs transversely across said an entire width of said insert and stops few millimeters short of a medial edge of said insert.
 14. A bicondylar femoral component as recited in claim 1, having a thin shell-like and compact convex articulating surface which covers only the weight bearing portion of the femoral articular surface wherein said femoral component only amenable for insertion into the knee through a true mini lateral approach.
 15. A tibial metallic component as recited in claim 1, having a transverse dovetail retaining ridge on bottom surface wherein said tibial component only amenable for insertion into the knee through a true mini lateral approach.
 16. A polyethylene insert as recited in claim 1, having a transverse dovetail retaining ridge which will transversally slide into a dovetail recess situated on the top surface of the metallic tibial tray, wherein said polyethylene insert is only amenable for insertion into the knee joint in a lateral sliding fashion through a true mini lateral approach.
 17. A knee resurfacing prosthesis as claimed in claim 1, wherein one or more vertical fins are integrally incorporated on the concave surface of the femoral component and the bottom surface of the tibia.
 18. The integral fins as recited in claim 17, where said fins may be incorporated not vertically but at 15° of inclination. 